The following structure is one of conventional structures for fixing a child seat, in which an infant may be seated, to a vehicle seat. The vehicle seat is previously provided with a latch member. The child seat is provided with a belt winder in which a belt is wound. The belt is withdrawn from the belt winder, the end of the belt is latched to the latch member, and the belt is then tightly wound by the belt winder (JPA 5-254367). In this conventional example, the belt is wound by gripping and turning a disk-like operating knob.
The conventional structure is inconvenient because it is necessary to strongly grip the operating knob for winding the belt.